(1) Isolation of a mutant from Escherichia coli K12 containing a temperature sensitive DNA adenine methylase mutation; (2) Purification of the DNA adenine methylase from Escherichia coli K12; (3) Mapping of the gene on the E. coli chromosome responsible for specifying the DNA adenine methylase. BIBLIOGRAPHIC REFERENCES: Marinus, M.G. and N.R. Morris (1975) Pleiotropic effects of a DNA adenine methylation mutation (dam-3) in Escherichia coli K12. Mutation Research 28: 15-26. Marinus, M.G., N.R. Morris, D. Soll and T.C. Kwong (1975) Isolation and partial characterization of three Escherichia coli mutants with altered transfer ribonucleic acid methylases. Journal of Bacteriology 122: 257-265.